The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides a multiple tube structure and methods of using same.
Cross-sectional area in a wellbore is a limited commodity. The wellbore must accommodate equipment and tubing strings passing therethrough, and must provide sufficient flow area for efficient production or injection of fluids therethrough.
In general, where multiple tubing strings are used in a single wellbore, conventional circular cross-section tubing strings have merely been positioned side-by-side in the wellbore. Although this may be the easiest solution, it is also very inefficient in utilizing the available cross-sectional area in the wellbore.
Another solution is to manufacture the tubing strings so that each has a generally D-shaped cross-section. When positioned side-by-side in the wellbore, the two tubing strings together have a generally circular cross-section and occupy a substantial portion of the cross-sectional area of the wellbore, and are therefore able to utilize more of this area for fluid flow, access, etc. Such a tube system is found in the Isolated Tie-Back System marketed by Sperry-Sun Drilling Services.
Although the D-shaped tubes used in the Isolated Tie-Back System represent a significant advance in the art, they do have a few disadvantages. One disadvantage is that the D-shaped tubes are somewhat expensive to manufacture. Another disadvantage is that they have not been designed to accommodate additional lines, such as electrical, hydraulic, fiber optic, etc., other than by placing these lines in the interiors of the tubes. Yet another, perhaps most important, disadvantage is that the D-shaped tubes have a relatively low burst and collapse strength as compared to a circular tube having equivalent cross-sectional area and wall thickness.
Therefore, it may be seen that it would be desirable to provide a multiple tube structure which both efficiently utilizes the available cross-sectional area in a wellbore, which accommodates additional lines therein and which has increased burst and collapse strength.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a tube system is provided which eliminates disadvantages in the art and permits multiple tubular members to be efficiently utilized in a well. Methods of positioning multiple tubular members in a well are also provided.
In one aspect of the invention, a tube system for use in a subterranean well is provided. The tube system includes multiple tubular members rigidly attached to each other along axial lengths thereof. The tubular members may be configured so that they conform to an interior of a generally D-shaped portion of a circle.
In another aspect of the invention, a method of positioning multiple tubular members in a well is provided. The method includes the steps of attaching the tubular members to each other along axial lengths thereof, and then positioning the attached tubular members in the well. The tubular members may be attached to each other so that the attached tubular members have a generally D-shaped cross-section.
In yet another aspect of the invention, the attached tubular members may be secured to a fluid conduit at ends thereof, so that the attached tubular members and the fluid conduit extend in the same axial direction. The fluid conduit may also be made up of a plurality of attached tubes. The attached tubular members may be positioned in one wellbore of the well, and the fluid conduit may be positioned in another wellbore of the well. The attached tubular members may be sealingly engaged with a sealing receptacle in one wellbore, while the fluid conduit is sealingly engaged with another sealing receptacle in the other wellbore.
These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of a representative embodiment of the invention hereinbelow and the accompanying drawings.